My understanding is that it's supposed to provide a 24mm FOV after in-camera distortion correction to a jpeg. When you take the undeveloped raw outside the camera, all bets are off on what you actually get. There is correction information built into the raw file, but it's up to the raw developer to use it properly.

Thanks Jim & James, that confirms my suspicion. This must mean this is a really bad ~22mm lens, and it also explains the poor corner performance. Mmmm I don't like how Panasonic relies on software correction when designing their lenses.